Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/06—Wet spinning methods
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof

Definitions

• the invention relates to a process for producing cellulosic fibers by forming a solution of cellulose in a tertiary amine oxide in the warm state into filaments, cooling the filaments and then introducing them into a precipitation bath in order to precipitate the dissolved cellulose, and a device for carrying them out of the procedure.
• tertiary amine oxides can dissolve cellulose and that cellulosic fibers can be obtained from these solutions by precipitation.
• a method for producing such solutions is known for example from EP-A - 0 356 419.
• a suspension of cellulose in an aqueous tertiary amine oxide is first prepared.
• the amine oxide contains up to 40% by mass of water.
• the aqueous cellulose suspension is heated and water is drawn off under reduced pressure until the cellulose dissolves.
• the process is carried out in a specially developed, evacuable stirring device.
• a process of the type mentioned at the outset is known from DE-A-28 30 635, according to which a solution of cellulose in a tertiary amine oxide is formed into filaments in a warm state, the filaments are cooled with air and then introduced into a precipitation bath in order to dissolve them To cut down cellulose. The surface of the spun threads is further wetted with water to reduce their tendency to stick to adjacent threads. It has been shown that all prior art processes are unsatisfactory with regard to filament formation and the textile properties of the fibers.
• This object is achieved in such a way that in a process for the production of cellulosic fibers in which a solution of cellulose in a tertiary amine oxide is formed into filaments in the warm state, the filaments are cooled and then introduced into a precipitation bath in order to precipitate the dissolved cellulose the shaped solution is exposed to an essentially laminar gas flow for cooling before being introduced into the precipitation bath.
• the invention is based on the knowledge that the textile properties of the fibers can be influenced by blowing with an inert gas, preferably air.
• the cooling process of the filament emerging from the spinneret affects not only the thread quality but also the stretching and stretching of the filaments. It has been shown according to the invention that fibers with uniform properties can be produced if the freshly extruded filaments are blown with a cooling gas stream which has as little turbulence as possible, that is to say is largely laminar. This leads to a decisive improvement in the spinning process.
• a preferred variant of the method according to the invention is that the laminar gas flow is directed essentially perpendicularly onto the filaments.
• the invention also relates to a device for carrying out the method according to the invention, which comprises a supply for cooling gas and a spinneret with spinning holes, which are arranged essentially in a ring to form an annular filament array, and is characterized in that the supply for cooling gas in the center of the the arrangement of the ring formed by the spinning holes is provided and the feed is designed in such a way that an essentially laminar gas flow strikes the filaments and the filaments are cooled with a laminar gas flow.
• the supply for cooling gas has a supply nozzle and an impact plate for deflecting the gas flow, the impact plate being designed in such a way that the gas flow remains as laminar as possible during the deflection.
• the invention further relates to the use of the device according to the invention for producing cellulosic fibers from a solution of cellulose in a tertiary amine oxide.
• FIG. 1 shows schematically the implementation of a dry / wet spinning process for producing cellulosic fibers according to the prior art
• FIG. 2a shows a preferred embodiment of the process according to the invention Show spinning device.
• FIG. 2b shows a section of FIG. 2a on an enlarged scale.
• 3 shows a device for comparison which does not have the features according to the invention.
• the pump 4 serves to meter the spinning mass and to set the pressure required for the extrusion.
• the thread structure extruded from the spinneret 1 via the spinning holes is designated by reference number 5.
• the thread bandage 5 enters the precipitation bath 6 via an air gap, which is defined by the distance of the spinneret 1 from the surface of the precipitation bath 6, is collected and pulled off via a deflection roller 7.
• the extruded thread bandage 5 is cooled with air, which is shown schematically in the figure with an arrow. A delay is achieved by pulling the thread assembly 5 over the roller 7 at a higher speed than it leaves the spinneret 1.
• FIG. 2a shows in section an annular, heatable (heating not shown) spinneret 1 'and a blowing device consisting of a central, tubular feed 8 for cooling gas and a baffle plate 9 for deflecting the gas flow from the vertical to a substantially horizontal direction .
• the ring-shaped spinneret 1 ' is fed at a point not shown in the drawing with spinning mass 3' which is spun into a dense, ring-shaped thread structure 5 'which is blown from the inside with cooling gas.
• the direction of blowing is indicated in the figure by means of a dashed arrow.
• the cooling air thus emerges from a circular sliding nozzle which is formed by the baffle plate 9 and by the counterpart 10.
• the gas flow strikes the plate-shaped baffle plate 9, is deflected horizontally, emerges as a laminar gas flow and strikes the ring-shaped thread structure 5 'on its inside.
• FIG. 2a The embodiment of the device according to the invention shown in FIG. 2a has a baffle plate for producing a laminar cooling gas flow, which deflects the vertical cooling gas flow without an abrupt transition into a substantially horizontal gas flow.
• FIG. 2b shows an enlarged view of that part of FIG. 2a that is provided for maintaining the laminar flow.
• the angles shown in FIG. 2b preferably have the following values: (baffle plate): ⁇ 12 * , preferably: 3 - 8 * ; ß (upper guide plate): ⁇ 10 * , preferably: 4 - 8 ";
• ⁇ S outer bead: ⁇ 30 ', preferably: 15-25 * ; ⁇ ( ⁇ + ß): ⁇ 22 * .
• An abrupt transition between the feed 8 and the baffle plate 9 leads to compression of the air jet with formation of high turbulence.
• Such a device which is not according to the invention, is shown in FIG. 3.
• the blowing device shown in FIG. 2b can either form a structural unit together with the spinneret 1 'or represent a separate component on which the ring-shaped spinneret 1' rests.
• An insulation (not shown) is expediently provided between the blowing device and the spinneret in order to prevent heat transfer from the spinning mass to the cooling air.
• the circular outlet slot opens at a total opening angle of ⁇ 22 'after the gas flow has been deflected.
• the steady increase in cross-section minimizes the flow resistances for the cooling gas.
• the small total opening angle prevents the cooling gas flow from coming off and enables the filaments to flow without turbulence.
• the gas flow after passing through the thread structure, returns partly warmed to the thread structure due to the formation of eddies, which leads to inadequate and irregular cooling.
• the result are different warping properties of the filament assembly, which can lead to a filament bundle which is unevenly loaded by the warping force and, as a result, to capillary cracks and to spinning disorders and sticking.
• a preferred embodiment of the device according to the invention has an annular bead 11, which slightly deflects the cooling gas flow that has passed through the thread structure downwards from the spinneret plane.
• a cellulose solution prepared according to the process described in EP-A-0 356 419 was filtered and spun in warm condition according to the process shown in FIG. 1, the spinning device being that in FIG. 2a and in the comparative example that in FIG Section shown device was used. Both devices had the same inner diameter of the tubular feed 8 for cooling gas (44 mm) and the same diameter of the baffle plate 9 (104 mm). In the example (device according to the invention), the angles ⁇ and ⁇ were each 5 * ; the total opening angle ⁇ was thus 10 * . The angle ⁇ 5 was 5 * .
• the table shows the mass of cellulose solution (kg / h) spun per hour for the example and for the comparative example, its composition (% by mass), its temperature ( * C) during spinning, the hole density (number of holes / ram 2 ) the spinneret, the diameter of the spinning holes ( ⁇ .), the nozzle warpage, the supply of cooling air (m 3 / h), its temperature ( * C), the temperature ( * C) the internal cooling air discharged, the fiber distortion, the NMMO content of the precipitation bath (mass% NMMO) and the final titer of the fibers produced (dtex).
• a nozzle draft ratio of 14.5: 1 could only be achieved with the blowing device according to the invention, the thread count being 1.18 dtex.
• the achievable thread count was about 20% less favorable.

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• 1993
  • 1993-07-01 AT AT0129193A patent/AT399729B/de not_active IP Right Cessation
• 1994
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